440 with a 595 CFM carb....?

[Cooter]

I guess in a perfect world, this would give good fuel economy, but performance has to suffer a little. I have a 650 DP i'm gonna run on my 440 with about 10-11 to 1 Compression and see if it works ok.

[c00nhunterjoe]

The carb will run as good as you tune it. A 500 cfm carb will be too lean. If its a very mild build, drop an 850 on it and TUNE it properly and you will get driveablility AND performance

[myk]

Weren't the stock carb's rated at about 700CFM or so?

[Chryco Psycho]

well lets look at this another way , the 1300 CFM 6 pack is rated at 3" of vacuum , the 4 bbls are rated at 1.5" vacuum & the 6 pack is approx 950 cfm rated at 1.5 " of vacuum .
So if you have maybe .5 inches of vacuum @ WOT how much air is a 1050 dominator flowing ??
My experience is 2x the CI , my 440 Duster went faster every time I increased carb size , the 1050 was the best combo .
The TQ was rated 800 CFM & was used ont he 340 /360 , 400 & 440 , the 1300 cfm 6 pack was also used on the 340 .
A 500 CFM on a 440 is the same as using a 2 bbl

[Cooter]

Weren't the stock carb's rated at about 700CFM or so?

Not sure on the AVS, but the AFB's were around 625 CFM...I know for a fact that an 850 DP will be WAY over carbed on thios engine. just too much. Not really lookin' for every last HP @ 9000 RPM or anything. By the formula, my 650 DP should be more than enough with the choke air horn milled off putting the SFM somewhere in the 700-725 CFM range.

I guess we'll see.

[BSB67]

.....my 440 Duster went faster every time I increased carb size ,

Exactly.  I have yet to slow a car down with a bigger carb.  I'm sure there is a point that it will hurt performance, but I can tell you that an 800 cfm double pump Holley carb on a stock 440 drives great and brings an increase in performance.

The 1967 440 AFB carbs are 750 cfm unless the cars were sold for use in California.

[c00nhunterjoe]

http://www.moparmusclemagazine.com/techarticles/engine/mopp_1207_carburetor_dyno_test/

Don't takemy word for it. The dyno doesn't lie. And all this on a cute little 383........ even slapped a 1050 dominator on it to see what would happen....... you wil be very surprised at the results across the board

[cdr]

http://www.moparmusclemagazine.com/techarticles/engine/mopp_1207_carburetor_dyno_test/

Don't takemy word for it. The dyno doesn't lie. And all this on a cute little 383........ even slapped a 1050 dominator on it to see what would happen....... you wil be very surprised at the results across the board

very good article to share for the naysayers

[John_Kunkel]

A 500 cfm carb will be too lean.

Not necessarily. If the carb is jetted to feed 500 cfm of air and that's all it will flow, the mixture will be correct. A carb that's too big will run leaner than a carb that's too small.

[elacruze]

Don't fail to consider a dual plane vs. single plane manifold. The single plane draws from all 4 venturis so all else being equal functions better with a smaller carb.

[BSB67]

A 500 cfm carb will be too lean.

Not necessarily. If the carb is jetted to feed 500 cfm of air and that's all it will flow, the mixture will be correct. A carb that's too big will run leaner than a carb that's too small.

John, I have to hand it to you for trying to explain this to people.  I gave up awhile ago.

[BSB67]

Don't fail to consider a dual plane vs. single plane manifold. The single plane draws from all 4 venturis so all else being equal functions better with a smaller carb.

Another one on the money that people don't even consider when talking carb size.  This has a real world impact.

[Chryco Psycho]

I would not run any 440 even stock with less than 800 CFM , the math formula doesn't work not because physics is off but because the air flow seems to be much lower than the rated carb flow at WOT with virtually 0 inches of vacuum . It is also possible to over fill a cylinder , mild supercharging just using cam overlap & high air flow speed .So it is possible to go past 100% VE at higher rpm without supercharging with good cam design & good head flow .

[c00nhunterjoe]

A 500 cfm carb will be too lean.

Not necessarily. If the carb is jetted to feed 500 cfm of air and that's all it will flow, the mixture will be correct. A carb that's too big will run leaner than a carb that's too small.

John, I have to hand it to you for trying to explain this to people.  I gave up awhile ago.

Perhaps my choice of words was poor, while you can jet a 500 cfm carb to have the correct V\E, it will still not deliver enough fuel to feed a 440.

If you are trying to put a 500 cfm carb on a 440 then perhaps you need to pull the 440 and drop a slant 6 in......

[BSB67]

A 500 cfm carb will be too lean.

Not necessarily. If the carb is jetted to feed 500 cfm of air and that's all it will flow, the mixture will be correct. A carb that's too big will run leaner than a carb that's too small.

John, I have to hand it to you for trying to explain this to people.  I gave up awhile ago.

Perhaps my choice of words was poor, while you can jet a 500 cfm carb to have the correct V\E, it will still not deliver enough fuel to feed a 440.

If you are trying to put a 500 cfm carb on a 440 then perhaps you need to pull the 440 and drop a slant 6 in......

Your choice of words is still poor.  I cannot tell if it is by accident or not.

A 500 CFM carb can easily deliver the proper air to fuel ratio to a 440.  The carbs ability to supply fuel is not the limiting factor.  The 500 cfm carb's hp potential is limited by how much air it can deliver under typical WOT operating conditions.  

[c00nhunterjoe]

What I am trying to say is that we are talking about putting a tiny carb on a big engine to get better fuel economy. Rather then try to essentially detune a big engine, which will reduce your horsepower, why not just put the smaller engine in the vehicle.  The carb rating is max flow anyway, which again, if we are looking for economy then you are not riding around wide open so what does it matter if you have a 500, 650,750 or a dominator on it? The "economical" driver would only be putt putting around just off idle all the time never utilizing the max cfm flow of whatever carb is on it. Furthermore, why are we even talking about a 4 barrel carb? Just remove it and drop a 2 barrel on it.

I am well aware of the technical side of properly tuning a carb(holleys anyway). Most people are not. Their knowledge stops at the idle screws. I saw no point in getting technical as most people don't follow it anyway.  We can debate the idea to death quoting dyno vaccum readings of the different size carbs at wot but again, that's about max power, which he is not looking for. The thought was smaller carb for smaller gas bill.

It doesn't matter what the size is, if it is jetted properly it will perform to its maximum potential on a given engine. You can say it however you like but again, we are talking max power to which,in theory, the secondaries will never open because we are looking for max economy, not max power and again, why are we talking about 4 barrels when you should just drop a 2 barrel on it if you want economy, and if you want economy, why is there a 440 in your car?

Sorry for the rant, been a long day, and I might have taken your reply the wrong way.

[FLG]

Question,

How much will a larger carb hurt throttle response? Not to mention how many people here run there car just at the track? Id say unless its a track only car you need to find a nice medium between throttle response/driveability and maximum power.

Personally i dont think the words fuel economy and carburetor should be in the same sentence, not to mention really anything about our cars in general (unless were talking SB that is taken out for parades or something). If you want better economy go with some kind of computer controlled injection that you can monitor and tune, could go from economic to performance with some software changes. But in the end is the few MPG really worth it? Probably not.

[c00nhunterjoe]

If you tune it properly it will be very responsive, crisp and smooth.

[Chryco Psycho]

It depend more on the carb then the size , I have used the 950 Proforms on 440 - 512 " engines & they have incredibly crisp throttle response . I also used a 1050 dominator on my 440 , I used to race it yes but I drove it 2+ HRS each way to the track & back & there was no issue with throttle response , this was on a Team G single plane highrise intake as well .
The smaller carbs will feed a proper mixture of fuel & air up to the limit of the airflow through the carb ,they will simply limit maximum air flow casuing the engine to lose power after they cannot feed anymore air that the engine wants/ needs .

[John_Kunkel]

If you tune it properly it will be very responsive, crisp and smooth.

Not from my experience, it might be crisp and responsive but not as crisp and responsive as a smaller carb. It's all about butterfly size and venturi size relating to velocity.

[c00nhunterjoe]

If you tune it properly it will be very responsive, crisp and smooth.

Not from my experience, it might be crisp and responsive but not as crisp and responsive as a smaller carb. It's all about butterfly size and venturi size relating to velocity.

The point was putting the carb that will give you your peak hp potential on your engine doesn't mean it won't be good on the street. As long as you tune it properly you won't sacrifice driveability.

[BSB67]

What I am trying to say is that we are talking about putting a tiny carb on a big engine to get better fuel economy. Rather then try to essentially detune a big engine, which will reduce your horsepower, why not just put the smaller engine in the vehicle.  The carb rating is max flow anyway, which again, if we are looking for economy then you are not riding around wide open so what does it matter if you have a 500, 650,750 or a dominator on it? The "economical" driver would only be putt putting around just off idle all the time never utilizing the max cfm flow of whatever carb is on it. Furthermore, why are we even talking about a 4 barrel carb? Just remove it and drop a 2 barrel on it.

I am well aware of the technical side of properly tuning a carb(holleys anyway). Most people are not. Their knowledge stops at the idle screws. I saw no point in getting technical as most people don't follow it anyway.  We can debate the idea to death quoting dyno vaccum readings of the different size carbs at wot but again, that's about max power, which he is not looking for. The thought was smaller carb for smaller gas bill.

It doesn't matter what the size is, if it is jetted properly it will perform to its maximum potential on a given engine. You can say it however you like but again, we are talking max power to which,in theory, the secondaries will never open because we are looking for max economy, not max power and again, why are we talking about 4 barrels when you should just drop a 2 barrel on it if you want economy, and if you want economy, why is there a 440 in your car?

Sorry for the rant, been a long day, and I might have taken your reply the wrong way.

I suggest that you go back and re-read the posts.

None of my posts regarding your incorrect statement have anything to do with good fuel economy or max hp.  It seems that you think they do.  The only reason I continue to respond is to help clear this up for those who don't understand the fundamentals of a carb.

Because you keep bringing it up, I'll respond to it.  There are applications where a 2 bbl, or a small 4 bbl is the best choice on a large displacement engine.   These are generally in rpm limited, full or nearly full load applications where a smaller displacement engine will not produce enough power.   And of course, these engines are not lean because of the carb size.  These applications are not as prevalent as they once were, as boosted smaller displacement engines or diesel engines are more the norm today.

[c00nhunterjoe]

I guess in a perfect world, this would give good fuel economy, but performance has to suffer a little. I have a 650 DP i'm gonna run on my 440 with about 10-11 to 1 Compression and see if it works ok.

This was the origonal post. Note what the 1st sentence says.

My choice for the use of the word lean was incorrect, the point is still the same. An 850 will only flow 850 cfm if you're wide open. Yes, an 850 will use more fuel wide open then a 595 wide open but if you're looking for fuel economy you are not wide open so its a mute point.

Also, as stated in cooter's 1st sentence, was max power would probably suffer. Yes, it will. A 595 carb can not adequately supply even a bone stock 440 with enough fuel to make its max power output.

I'm done with the conversation. Its getting me nowhere but frustrated.

[BSB67]

I guess in a perfect world, this would give good fuel economy, but performance has to suffer a little. I have a 650 DP i'm gonna run on my 440 with about 10-11 to 1 Compression and see if it works ok.

This was the origonal post. Note what the 1st sentence says.

My choice for the use of the word lean was incorrect, the point is still the same. An 850 will only flow 850 cfm if you're wide open. Yes, an 850 will use more fuel wide open then a 595 wide open but if you're looking for fuel economy you are not wide open so its a mute point.

Also, as stated in cooter's 1st sentence, was max power would probably suffer. Yes, it will. A 595 carb can not adequately supply even a bone stock 440 with enough fuel to make its max power output.

I'm done with the conversation. Its getting me nowhere but frustrated.

I don't mean to frustrate you.  But frankly do not understand why you are.  Here is your comment that I have been responding to: "A 500 cfm carb will be too lean", and it has nothing to do with Cooters post.  You have read way more into it.

[71bee]

Weren't the stock carb's rated at about 700CFM or so?

The stock AFB & AVS carbs were rated @ 625 CFM (340-383) & 750 CFM (413-440). I have re-built a few Holley 4160 carbs for early C bodies running a low performance 440 that were rated @ 575 CFM.